Prostate cancer (PCa) is one of the most frequently diagnosed noncutaneous cancers among men in the US and is the second most common cause of cancer deaths with more than 200,000 new cases and over 30,000 deaths each year in the United States. PCa therapeutics market is growing at an annual rate of 15-20% globally.
Androgen-deprivation therapy (ADT) is the standard of treatment for advanced PCa. Patients with advanced prostate cancer undergo ADT, either by luteinizing hormone releasing hormone (LHRH) agonists, LHRH antagonists or by bilateral orchiectomy. Despite initial response to ADT, disease progression is inevitable and the cancer emerges as castration-resistant prostate cancer (CRPC). Up to 30% of patients with prostate cancer that undergo primary treatment by radiation or surgery will develop metastatic disease within 10 years of the primary treatment. Approximately 50,000 patients a year will develop metastatic disease, which is termed metastatic CRPC (mCRPC).
Patients with CRPC have a median survival of 12-18 months. Though castration-resistant, CRPC is still dependent on the androgen receptor (AR) signaling axis for continued growth. The primary reason for CRPC re-emergence is re-activation of AR by alternate mechanisms such as 1) intracrine androgen synthesis, 2) AR splice variants (AR-SV) that lack ligand binding domain (LBD), 3) AR-LBD mutations with potential to resist AR antagonists (i.e., mutants that are not sensitive to inhibition by AR antagonists, and in some cases AR antagonists act as agonists of the AR bearing these LBD mutations); and 4) amplications of the AR gene within the tumor.
A critical barrier to progress in treating CRPC is that AR signaling inhibitors such as enzalutamide, bicalutamide, and abiraterone, acting through the LBD, fail to inhibit growth driven by the N-terminal domain (NTD)-dependent constitutively active AR-SV such as AR-V7, the most prominent AR-SV. Recent high-impact clinical trials with enzalutamide and abiraterone in CRPC patients demonstrated that just 13.9% of AR-V7-positive patients among 202 patients starting treatment with enzalutamide (Xtandi) or abiraterone acetate (Zytiga) had PSA responses to either of the treatments (Antonarakis ES, Lu C, Luber E, et al. J. Clin. Oncol. 2017 April 6. doi: 25 10.1200/JCO0.2016.70.1961), indicating the requirement for next generation AR antagonists that target AR-SVs. In addition, a significant number of CRPC patients are becoming refractory to abiraterone or enzalutamide, emphasizing the need for next generation AR antagonists.
Current evidences demonstrate that CRPC growth is dependent on constitutively active AR including AR-SV's that lack the LBD such as AR-V7 and therefore cannot be inhibited by conventional antagonists. AR inhibition and degradation through binding to a domain that is distinct from the AR LBD provides alternate strategies to manage CRPC.
Herein the NTD is biophysically characterized to interact with the SARDs of this invention via fluorescence polarization (FP; Example 11 and FIG. 11) and biolayer interferometry (Example 12 and FIG. 12). Biochemical evidence also supports the SARDs of this invention binding to a domain other than the LBD. E.g., SARDs of this invention degrade AR-SV in 22RV-1 cells expressing AR-V7 (FIGS. 3 and 10). Eurther, the R- and S-isomers of the SARDs of this invention possess equipotent SARD activity despite demonstrated differences in the binding and inhibition of androgen-dependent transactivation via the LBD. The report of SARD activity mediated through the NTD of AR is an unprecedented observation that may help explanation the prodigious AR antagonism profiles seen with the SARDs of this invention.
Molecules that degrade the AR prevent any inadvertent AR activation through growth factors or signaling pathways, or promiscuous ligand-dependent activation. In addition, molecules that inhibit the constitutive activation of AR-SVs are extremely important to provide extended benefit to CRPC patients.
Currently only a few chemotypes are known to degrade AR which include the SARDs ARN-509, AZD-3514, and ASC-J9. However, these molecules degrade AR indirectly at much higher concentrations than their binding coefficient and they fail to degrade the AR-SVs that have become in recent years the primary reason for resurgence of treatment-resistant CRPC.
This invention describes novel AR antagonists with unique pharmacology that strongly (high potency and efficacy) and selectively bind AR (better than known antagonists; bind to LBD and/or NTD), antagonize AR, and degrade AR full length (AR-FL) and AR-SV. Selective androgen receptor degrader (SARD) compounds possess dual degradation and AR-SV inhibitory functions and hence are distinct from any available CRPC therapeutics. These novel selective androgen receptor degrader (SARD) compounds inhibit the growth of PCa cells and tumors that are dependent on AR-FL and AR-SV for proliferation.
SARDs have the potential to evolve as new therapeutics to treat CRPCs that are untreatable with any other antagonists. This unique property of degrading AR-SV has extremely important health consequences for prostate cancer. Till date only one series of synthetic molecules (EPI-001, EPI-506, etc.) and some marine natural products such as the sinkotamides and glycerol ether Naphetenone B, are reported to bind to AR-NTD and inhibit AR function and PCa cell growth, albeit at lower affinity and inability to degrade the receptor. The SARDs reported herein also bind to AR-NTD and inhibit NTD-driven (e.g., ligand independent) AR activity.
The positive correlation between AR and PCa and the lack of a fail-safe AR antagonist, emphasize the need for molecules that inhibit AR function through novel or alternate mechanisms and/or binding sites, and that can elicit antagonistic activities within an altered cellular environment.
Although traditional antiandrogens such as enzalutamide, bicalutamide, apalutamide and flutamide and androgen deprivation therapies (ADT) were approved for use in prostate cancer, there is significant evidence that antiandrogens could also be used in a variety of other hormonal dependent and hormone independent cancers. For example, antiandrogens have been tested in breast cancer (enzalutamide; Breast Cancer Res. (2014) 16(1): R7), non-small cell lung cancer (shRNAi AR) (Mol. Cell Endocrinol. 2010, 317(1-2):14-24), renal cell carcinoma (ASC-J9) (Cancer Res. 2014, 74(16):4420-30), partial androgen insensitivity syndrome (PAIS) associated malignancies such as gonadal tumors and seminoma, advanced pancreatic cancer (World J. Gastroenterology 20(29):9229), cancer of the ovary, fallopian tubes (ClinicalTrials.gov, Identifier: NCT01974765), or peritoneum, cancer of the salivary gland (Head and Neck (2016) 38: 724-731; ADT was tested in AR-expressing recurrent/metastatic salivary gland cancers and was confirmed to have benefit on progression free survival and overall survival endpoints), esophageal cancer (World J. Gastroenterol, 2015, 21(20):6146-56), bladder cancer (Oncotarget 6 (30): 29860-29876; Int J. Endocrinol (2015), Article ID 384860), pancreatic cancer, lymphoma (including mantle cell) (Exp. Hematol. 2017, 49:34-38.e2), melanoma (Melanoma Res. 2002, 12(6):529-38), gastric cancer (J. Cancer Res. Clin. Oncol. 2004, 130(5):253-8), colon cancer (Virchows Arch B Cell Pathol. Incl. Mol. Pathol. 1982, 38(3):351-5), and hepatocellular carcinoma (World J. Gastroenterol. 2014, 20(28):9229-36). Use of a more potent antiandrogen such as a SARD in these cancers may treat the progression of these and other cancers. Many hormonal and non-hormonal cancers may benefit from SARD treatment such as breast cancer, testicular cancer, cancers associated with partial androgen insensitivity syndromes (PAIS) such as gonadal tumors and seminoma, uterine cancer, ovarian cancer, cancer of the fallopian tubes or peritoneum, salivary gland cancer, bladder cancer, urogenital cancer, brain cancer, skin cancer, lymphoma, melanoma, mantle cell lymphoma, liver cancer, hepatocellular carcinoma, renal cancer, renal cell carcinoma, osteosarcoma, pancreatic cancer, esophageal cancer, endometrial cancer, lung cancer, non-small cell lung cancer (NSCLC), gastric cancer, colon cancer, perianal adenoma, or central nervous system cancer.
Triple negative breast cancer (TNBC) is a type of breast cancer lacking the expression of the estrogen receptor (ER), progesterone receptor (PR), and HER2 receptor kinase. As such, TNBC lacks the hormone and kinase therapeutic targets used to treat other types of primary breast cancers. Correspondingly, chemotherapy is often the initial pharmacotherapy for TNBC. Interestingly, AR is often still expressed in TNBC and may offer a hormone targeted therapeutic alternative to chemotherapy. In ER-positive breast cancer, AR is a positive prognostic indicator as it is believed that activation of AR limits and/or opposes the effects of the ER in breast tissue and tumors. However, in the absence of ER, it is possible that AR actually supports the growth of breast cancer tumors. Though the role of AR is not fully understood in TNBC, we have evidence that certain TNBC's may be supported by androgen independent activation of AR-SVs lacking the LBD or androgen-dependent activation of AR full length (see US2017/0368003A1). As such, enzalutamide and other LBD directed traditional AR antagonists would not be able to antagonize AR-S Vs in these TNBC's. However, SARDs of this invention which are capable of destroying AR-SVs (Example 3 and FIGS. 3 and 10) through a binding site in the NTD of AR (see Examples 11 and 12) would be able to antagonize AR including AR-SV observed in TNBC patient derived xenograpfts and provide an anti-tumor effect.
Traditional antiandrogens such as bicalutamide and flutamide were approved for use in prostate cancer. Subsequent studies have demonstrated the utility of antiandrogens (e.g., flutamide, spironolactone, cyproterone acetate, finasteride and chlormadinone acetate) in androgen-dependent dermatological conditions such as androgenic alopecia (male pattern baldness), acne vulgaris, and hirsutism (e.g., in female facial hair). Prepubertal castration prevents sebum production and androgenic alopecia but this can be reversed by use of testosterone, suggesting its androgen-dependence.
The AR gene has a polymorphism of glutamine repeats (polyQ) within exon 1 which when shortened may augment AR transactivation (i.e., hyperandrogenism). It has been found that shortened polyQ polymorphisms are more common in people with alopecia, hirsutism, and acne. Classic antiandrogens are undesirable for these purposes because they are ineffective through dermal dosing and their long-term systemic use raises the risks of untoward sexual effects such as gynecomastia and impotence. Further, similar to CPRC discussed above, inhibition of ligand-dependent AR activity alone may not be sufficient as AR can be activated by various cellular factors other than the endogeneous androgens testosterone (T) and dihydrotestosterone (DHT), such as growth factors, kinases, co-activator overexpression and/or promiscuous activation by other hormones (e.g., estrogens or glucocorticoids). Consequently, blocking the binding of T and DHT to AR with a classical antiandrogen may not be sufficient to have the desired efficacy.
An emerging concept is the topical application of a SARD to destroy the AR locally to the affected areas of the skin or other tissue without exerting any systemic antiandrogenism. For this use, a SARD that does not penetrate the skin or is rapidly metabolized would be preferrable.
Supporting this approach is the observation that cutaneous wound healing has been demonstrated to be suppressed by androgens. Castration of mice accelerates cutaneous wound healing while attenuating the inflammation in the wounds. The negative correlation between androgen levels and cutaneous healing and inflammation, in part, explains another mechanism by which high levels of endogenous androgens exacerbate hyperandrogenic dermatological conditions. Further, it provides a rationale for the treatment of wounds such as diabetic ulcers or even trauma, or skin disorders with an inflammatory component such as acne or psoriasis, with a topical SARD.
Androgenic alopecia occurs in ˜50% of Caucasian males by midlife and up to 90% by 80 years old. Minoxidil (a topical vasodilator) and finasteride (a systemic 5alpha reductase type II inhibitor) are FDA approved for alopecia but require 4-12 months of treatment to produce a therapeutic effect and only arrest hair loss in most with mild to moderate hair regrowth in 30-60%. Since currently available treatments have slow and limited efficacy that varies widely between individuals, and produce unwanted sexual side effects, it is important to find a novel approach to treat androgenic alopecia and other hyperandrogenic dermatologic diseases.
Anti-androgens are effective in hyperandrogenic hormonal conditions in females such as precocious puberty, early puberty, dysmenorrhea, amenorrhea, multilocular uterus syndrome, endometriosis, hysteromyoma, abnormal uterine bleeding, early menarche, fibrocystic breast disease, fibroids of the uterus, ovarian cysts, polycystic ovary syndrome, pre-eclampsia, eclampsia of pregnancy, preterm labor, premenstrual syndrome, and/or vaginal dryness. These hormonal conditions are hyperandrogenic. For example, hyperandrogenic central precocious puberty (CPP) is discussed in Pediatric Research (1993) 33, S14-S14 or in the Pediatric Research supplement (abstract 64) and others are known in the art.
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease. Patients with ALS are characterized by extended AR polyglutamine repeats. Riluzole is an available drug for ALS treatment, however, only provides short-term effects. There is an urgent need for drugs that extend the survival of ALS patients. Transgenic animals of ALS were shown to survive longer upon castration and reduction in AR levels compared to castration+nandrolone (agonist) supplementation. Castration reduces the AR level, which may be the reason for extended survival.
Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by selective loss of upper and lower motor neurons and skeletal muscle atrophy. Epidemiologic and experimental evidence suggest the involvement of androgens in ALS pathogenesis (“Anabolic/androgenic steroid nandrolone exacerbates gene expression modifications induced by mutant SOD1 in muscles of mice models of amyotrophic lateral sclerosis.” Galbiati M, Onesto E, Zito A, Crippa V, Rusmini P, Mariotti R, Bentivoglio M, Bendotti C, Poletti A. Pharmacol. Res. 2012, 65(2), 221-230), but the mechanism through which androgens modify the ALS phenotype is unknown. A transgenic animal model of ALS demonstrated improved survival upon surgical castration {i.e., androgen ablation). Treatment of these castrated animals with the androgen agonist nandrolone decanoate worsened disease manifestations. Castration reduces the AR level, which may be the reason for extended survival. The survival benefit is reversed by androgen agonist (“Androgens affect muscle, motor neuron, and survival in a mouse model of SOD1-related amyotrophic lateral sclerosis.” Aggarwal T, Polanco M J, Scaramuzzino C, Rocchi A, Milioto C, Emionite L, Ognio E, Sambataro E, Galbiati M, Poletti A, Pennuto M. Neurobiol. Aging. 2014 35(8), 1929-1938). Notably, stimulation with nandrolone decanoate promoted the recruitment of endogenous androgen receptor into biochemical complexes that were insoluble in sodium dodecyl sulfate, a finding consistent with protein aggregation. Overall, these results shed light on the role of androgens as modifiers of ALS pathogenesis via dysregulation of androgen receptor homeostasis. Antiandrogens should block the effects of nandrolone undecanoate or endogeneous androgens and reverse the toxicities due to AR aggegregation. Eurther, an antiandrogen that can block action of LBD-dependent AR agonists and concomitantly lower AR protein levels, such as the SARDs of this invention, would be therapeutic in ALS. Riluzole is an available drug for ALS treatment, however, it only provides short-term effects. There is an urgent need for drugs that extend the survival of ALS patients.Uterine fibroids are also known as leiomyoma. Androgens promote uterine proliferation and the formation of leiomyoma. Leiomyoma has been associated with increased mutations in polyQ AR (J. Assist. Reprod. Genet. 2004, 21(12), 453-457; Clin. Chem. Lab. Med. 2008, 46(6), 814-823). Degradation of the pathogenic polyQ AR may be preventative of and therapeutic in leiomyomas. For example, the SWAN study (J. Clin. Endocrinol. Metab. 2016, 101(1), 123-130) established that middle aged women with high testosterone had a 33% increased incidence of new uterine fibroids and the risk was further elevated to 52% in those with high testosterone and estradiol.
Androgen receptor action promotes uterine proliferation. Hyperandrogenicity of the short polyQ AR has been associated with increased leiomyoma or uterine fibroids. (Hsieh Y Y, Chang C C, Tsai E J, Lin C C, Yeh L S, Peng C T. J. Assist. Reprod. Genet. 2004, 21(12), 453-457). A separate study of Brazilian women found that shorter and longer [CAG](n) repeat alleles of AR were exclusive to the leiomyoma group in their study (Rosa E E, Canevari Rde A, Ambrosio E P, Ramos Cirilo P D, Pontes A, Rainho C A, Rogatto S R. Clin. Chem. Lab. Med. 2008, 46(6), 814-823). Similarly, in Asian Indian women long polyQ AR was associated with endometriosis and leiomyoma and can be regarded as high-risk markers. SARDs could be used in women with uterine fibroids, especially those expressing shorter and longer [CAG](n) repeat alleles, to treat existing uterine fibroids, prevent worsening of fibroids and/or ameliorate carcinogenicity associated with fibroids. An abdominal aortic aneurysm (AAA) is an enlarged area in the lower part of the aorta, the major blood vessel that supplies blood to the body. The aorta, about the thickness of a garden hose, runs from your heart through the center of your chest and abdomen. Because the aorta is the body's main supplier of blood, a ruptured abdominal aortic aneurysm can cause life-threatening bleeding. Depending on the size and the rate at which your abdominal aortic aneurysm is growing, treatment may vary from watchful waiting to emergency surgery. Once an abdominal aortic aneurysm is found, doctors will closely monitor it so that surgery can be planned if it's necessary. Emergency surgery for a ruptured abdominal aortic aneurysm can be risky. AR blockade (pharmacologic or genetic) reduces AAA. Davis et al. (Davis J P, Salmon M, Pope N H, Lu G, Su G, Meher A, Ailawadi G, Upchurch G R Jr. J Vasc Surg (2016) 63(6):1602-1612) showed that flutamide (50 mg/kg) or ketoconazole (150 mg/kg) attenuated porcine pancreatic elastase (0.35 U/mL) induced AAA by 84.2% and 91.5% compared to vehicle (121%). Further AR−/− mice showed attenuated AAA growth (64.4%) compared to wildtype (both treated with elastase). Correspondingly, administration of a SARD to a patient suffering from an AAA may help reverse, treat or delay progression of AAA to the point where surgery is needed.
X-linked spinal-bulbar muscular atrophy (SBMA—also known as Kennedy's disease) is a muscular atrophy that arises from a defect in the androgen receptor gene on the X chromosome. Proximal limb and bulbar muscle weakness results in physical limitations including dependence on a wheelchair in some cases. The mutation results in a protracted polyglutamine tract added to the N-terminal domain of the androgen receptor (polyQ AR). Binding and activation of this lengthened polyQ AR by endogeneous androgens (testosterone and DHT) results in unfolding and nuclear translocation of the mutant androgen receptor. The androgen-induced toxicity and androgen dependent nuclear accumulation of polyQ AR protein seems to be central to the pathogenesis. Therefore, the inhibition of the androgen-activated polyQ AR might be a therapeutic option (A. Baniahmad. Inhibition of the androgen receptor by antiandrogens in spinobulbar muscle atrophy. J. Mol. Neurosci. 2016 58(3), 343-347). These steps are required for pathogenesis and result in partial loss of transactivation function (i.e., an androgen insensitivity) and a poorly understood neuromuscular degeneration. Support of use antiandrogen comes in a report in which the antiandrogen flutamide protects male mice from androgen-dependent toxicity in three models of spinal bulbar muscular atrophy (Renier K J, Troxell-Smith S M, Johansen J A, Katsuno M, Adachi H, Sobue G, Chua J P, Sun Kim H, Lieberman A P, Breedlove S M, Jordan C L. Endocrinology 2014, 155(7), 2624-2634). Currently there are no disease-modifying treatments but rather only symptom directed treatments. Efforts to target the polyQ AR of Kennedy's disease as the proximal mediator of toxicity by harnessing cellular machinery to promote its degradation, i.e., through the use of a SARD, hold promise for therapeutic intervention. Selective androgen receptor degraders such as those reported herein bind to and degrade all androgen receptors tested (full length, splice variant, antiandrogen resistance mutants, etc.) so degradation of polyQ AR polymorphism is also expected, indicating that they are promising leads for treatment of SBMA.
Here we describe 3-amino-propanamide SARDs that bind to LBD and an alternate binding and degradation domain (BDD; located in the NTD), antagonize AR, and degrade AR thereby blocking ligand-dependent and ligand-independent AR activities. This novel mechanism produces improved efficacy when dosed systemically (e.g., for prostate cancer) or topically (e.g., dermatological diseases).